In a wind turbine, electric energy is generated using a generator from a rotational movement of a rotor shaft, which is driven by a rotor. Depending on the available range of rotational speeds, different types of generators are used in view of an efficient generation of energy. These types differ significantly with respect to their sizes and the use of material and production expense, which are required for their manufacture. In order to make possible the use of generators which are as compact as possible, and as inexpensive as possible to manufacture, wind turbines are therefore often equipped with transmissions, which translate the rotational speed of the rotor shaft to a range of rotational speeds, for which a desired type of generators is suitable. In view of the enormous forces and torques, which occur in particular in high-power wind turbines, i.e. in the MW range, planetary transmissions have proven to be particularly suitable.
The gears of the planetary transmission used are rotatably supported in part by rolling-element bearings. Thus for example the planetary gears of a planetary transmission used in wind turbines are rotatably supported by a bearing assembly which includes a plurality of outer rings that are disposed axially adjacent. The outer rings are disposed in a bore of the planetary gear and are connected to the planetary gear by a press-fit so that they rotate together. In addition, the outer rings are secured against axial displacement by a spring ring which is disposed between adjacent outer rings and engages in a radial groove in the planetary gear. Despite the rotationally-fixed connection of the outer rings to the planetary gear, a migration of the outer rings can occur. This migration can sometimes lead to significant wear of the spring ring which is axially adjacent to the outer rings, even though only relatively small axial forces are to be expected in the constructions used. Wear of the spring ring can for example lead to consequential damages to the entire bearing assembly by separated chips.
The problems caused by the migration of the outer rings can for example be avoided by omitting the outer rings and the spring ring and by forming the rolling-element bearing raceways and the stop flange as one-part with the planetary gear. However, with respect to good operating properties and a long service life, such a design sets minimum requirements on the material composition of the planetary gear, at least in the region of the rolling-element raceways. In addition, a relatively expensive processing of the planetary gear is required in general to form a suitable geometry of the rolling-element bearing raceways and of the stop flanges, as well as a suitable surface finish. The requirements and the expense can be held somewhat lower if one keeps the outer rings and merely replaces the spring ring with a spacer ring which is formed as one-part with the planetary gear.